The invention relates to an elongate construction element. Such construction elements are used frequently, but not exclusively, in the construction industry. Reference may be made, for example, to timber formwork girders, such as are used for example for supporting formwork sheets in floor formwork. They are of I-section, that is to say have two outer webs, which extend perpendicularly to the system plane, as well as one inner web. The lengths lie in the range of about 2.5 m-6 m. They weigh 5-6 kg/m, have an allowable moment in the range of 5 KNm and an allowable transverse force of 11 KN. The widths are around 8 cm and the heights in the range of 16-20 cm. These timber girders are suitable for static loads. Wood is typically not suitable for accepting dynamic loads. Metal is used for accepting dynamic loads. The known timber formwork girders are at least partly glued from laminated wood. This entails a whole series of disadvantages: wood is expensive and less and less available. On the other hand, many are glad if plastics scrap is no longer dumped on refuse sites but can be reused. However, the price of virgin plastic is also dropping continually and new mineral oil sources are being discovered all the time, so that it seems that supplies are assured for several centuries. Disposal of the wood poses problems, because it cannot simply be burned on account of its phenolic resin gluing and its impregnation against insect and fungal attack. Also, some refuse sites no longer accept this wood. Such girders have to be nailed, whether it is to join them to the formwork sheets or whether they have to be nailed to the girder forks. The wood may be mechanically damaged during nailing by splitting. The same applies if it is dropped on the construction site. The material is influenced by weathering and water absorption. In spite of great efforts, the allowable moment and the allowable transverse force are low, but the weight high.
The same also applies in principle with respect to boards or sheets of wood, such as for example formwork sheets.
There are also T girders, angle sections, square beams or suchlike construction elements, where the same disadvantages occur.
In addition, elongate construction elements are also used as supports, which are subjected to compression and buckling force, such as for example the supports for such ceiling formwork. Such construction elements are produced nowadays from galvanized steel tubes. Hot galvanizing is expensive and harmful to the environment. It is difficult to verify whether the tubes have been galvanized on the inside. If the tubes are bent, they no longer run one in the other and their disposal is also expensive.
There are also construction elements which, until now, have been sheathed in plastic in order to protect them, for example, against aggressive liquids. In spite of the sheathing, these construction elements have scarcely improved dimensional stability.